30 May 2017 Thermoelectric bolometers based on silicon membranes
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State-of-the-art high performance IR sensing and imaging systems utilize highly expensive photodetector technology, which requires exotic and toxic materials and cooling. Cost-effective alternatives, uncooled bolometer detectors, are widely used in commercial long-wave IR (LWIR) systems. Compared to the cooled detectors they are much slower and have approximately an order of magnitude lower detectivity in the LWIR. We present uncooled bolometer technology which is foreseen to be capable of narrowing the gap between the cooled and uncooled technologies. The proposed technology is based on ultra-thin silicon membranes, the thermal conductivity and electrical properties of which can be controlled by membrane thickness and doping, respectively. The thermal signal is transduced into electric voltage using thermocouple consisting of highly-doped n and p type Si beams. Reducing the thickness of the Si membrane improves the performance (i.e. sensitivity and speed) as thermal conductivity and thermal mass of Si membrane decreases with decreasing thickness. Based on experimental data we estimate the performance of these uncooled thermoelectric bolometers.
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Aapo Varpula, Aapo Varpula, Andrey V. Timofeev, Andrey V. Timofeev, Andrey Shchepetov, Andrey Shchepetov, Kestutis Grigoras, Kestutis Grigoras, Jouni Ahopelto, Jouni Ahopelto, Mika Prunnila, Mika Prunnila, } "Thermoelectric bolometers based on silicon membranes", Proc. SPIE 10246, Smart Sensors, Actuators, and MEMS VIII, 102460L (30 May 2017); doi: 10.1117/12.2266554; https://doi.org/10.1117/12.2266554

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